Nothing was said about a "substitute" 1099-R which is not appropriate. A substitute (form 4852) is used to *correct* a defective 1099-R that you *received* and the issuer refused to correct. You do not have a 1099-R to substitute for.
You are just entering an *original* 1099-R early that is all.
If you are not comfortable doing that, then just wait for the real 1099-R next year, and then amend 2020 to report it. Entering it early just saves the trouble of amending next year.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
